In order to reduce the number of accidental poisonings resulting from young children having access to unsafe medicines, drugs, household chemicals and other products, there has been considerable activity in recent years toward the development of closures and containers in which a type of manipulation between the cap and container is required in order to gain access to the contents of the container that a young child is incapable of performing. For example, it has been found that young children are generally incapable of manipulating a cap mounted on a container bayonet type locking means--a type of locking means which requires that the cap be pushed relative to the container and then rotates relative to the container in order to separate the cap from the container. The cap must be pushed axially toward the container against the biasing force of a spring-like element in order to disengage the bayonet locking means. See, for example, Hedgewick U.S. Pat. No. Re. 27,156.
There are many caps of the type having an inner cap adapted to threadedly engage the neck portion of a container and an outer cap fixedly attached over the inner cap to prevent external access thereto. The outer cap is generally spring-biased away from the cap to provide relatively free rotation therebetween. Upon pushing the outer cap toward the inner cap, the two caps engage in some manner so as to produce rotation of the inner cap with the outer cap and allow unthreading thereof. Examples of such caps are disclosed in U.S. Pat. Nos. 2,964,207, 3,374,912, 3,394,829, 3,396,864, 3,764,033, 3,853,236, 3,857,505 and 3,944,102. A problem with many of such closures is that they cannot be applied with conventional capping machinery.
Another problem is that it is difficult to produce such closures by mass production molding and assembly techniques because of their structural design. Other problems result when the two parts forming the closure include unnecessary material. If the two parts do not fit correctly with respect to each other, cocking occurs and the closure will often fail as the mating and/or engaging portions of the inner and outer caps become excessively worn.
Other patents to which this invention generally relates are U.S. Pat. Nos. 3,432,065, 3,753,510, 4,002,259 and 4,042,028.